Device and method of determining arterial wall elasticity

ABSTRACT

A new and original indirect method of determining arterial wall elasticity is described. The speed of the transmission of the pulse wave between two points in the arterial system, i.e., the left external carotid and left dorsalis pedis arteries, is measured. The faster the transmission of the pulse wave, the less elastic is the arterial wall. The time of the transmission of the pulse wave is measured by recording the arterial pulses in the left external carotid and left dorsalis pedis arteries with a device, which I originally designed and described in detail above, attached to the center of the pick up microphone of a high frequency oscillograph, simultaneously with the Std. Lead II of the ECG. The device produces pulses which very closely resemble the intra arterial pulses and this is essential as said pulses have foot points which are easily distinguishable and marked as reference points for accurate time interval measurements. In this method a longer segment of the arterial system is measured so that the margin of error for statistical analysis is loss. This method is original as the “peripheral artery” used is the left dorsalis pedis artery and this has never been mentioned in the medical literature up to the present. Also, the segment from the left external carotid artery to the left dorsalis pedis artery is an original idea, as the medical literature up to present describes segments from the left external carotid artery to the left femoral artery or from the external carotid artery to the brachial or radial arteries which are shorter segments compared to that of my method.

The present invention relates to medical technology but moreparticularly, to a device and method of determining the elasticity ofthe arterial wall.

BACKGROUND OF THE INVENTION

I have been working on the oscillographic method of recording arterialpulses for many years now. When I started doing researches onhaemodynamics, particularly pulse wave velocity, for which I was granteda Fellowship by the International Federation of University Women, I wasconfronted with the problem of recording arterial pulses which resembledthe intra arterial pulses as closely as possible. This was essential asthese said pulses showed the foot points or starting points of therecorded pulses which serve as reference points and which are marked fortime interval measurements. After many repeated trials, I was able todesign an attachment to the pickup microphone of the NEP pulse recordingunit (Type A-643) of Sanborn. This attachment enabled me to record thedesired pulses described above so that I was able to continue with myresearches on pulse wave velocity. Said attachment is described indetail below.

In determining the elasticity of the arterial wall indirectly bymeasuring the time of the transmission of the pulse wave through thearteries, we use a “central artery” and a “peripheral artery” asreference points. The time interval between the instant the pulse isrecorded in the “central artery” and the instant that the same pulse isrecorded in the “peripheral artery”, is a measure of the time delaybetween the two reference points. In the medical literature, the leftexternal carotid artery has always been used as the “central artery” andthe left femoral, brachial, radial or other arteries have been used asthe “peripheral artery”. The use of the left dorsalis pedis artery as a“peripheral artery” has never been mentioned in the medical literatureup to the present. It was my original idea to make use of the dorsalispedis artery as the “peripheral artery” on the assumption that I will bemeasuring a longer segment of the arterial system so that the margin oferror for statistical analysis is less. Also, this artery is wellexposed and easy to locate so that the sensor can be placed over it withease.

Compared to other non invasive methods of measuring the pulse wavevelocity (Doppler flow, ultrasounds and magnetic resonance) my deviceand method are simple, easy and fast to perform, reproducible,relatively inexpensive, compact and portable so that it is very suitablefor epidemiologic studies in large populations especially in developingcountries.

BRIEF SUMMARY OF THE INVENTION

The primary object of this invention is to introduce a new device and anoriginal method which has never been described in the medical literaturefor indirectly determining the elasticity of the arterial wall on aliving subject.

The left external carotid artery as the “central artery” has beendescribed by many authors, but the use of the left dorsalis pedis arteryas the “peripheral artery” is my original idea and has not beenmentioned in the medical literature up to the present. These arteriesare well exposed, easily located and the distance between them is muchlonger compared to other methods heretofore described. The longersegment measured makes the margin or error for statistical analysisless, The subjects used for these studies are within a specific heightrange.

It is essential that the pulses recorded resemble as closely as possiblethe intra arterial pulse so that the foot points are clearlydistinguishable as they are marked and used as reference points for timeinterval measurements. This has been achieved by using a special devicethat I have originally designed to be attached to the pick up microphoneof the high frequency oscillograph. Specifically, the device is acircular metallic plate, one centimeter in diameter and one millimeterthick whose center is welded to the center of the pick up microphonewith a solid tubular rod, one centimeter long and one millimeter indiameter. This device is placed on the skin over the artery. Theanacrotic pulses recorded distinctly shows the foot points which serveas reference points in measuring the distances between the pulses of theleft external carotid (“central artery”) and left dorsalis pedis(“peripheral artery”).

BRIEF DESCRIPTION OF FIGURES

FIG. 1 is a perspective view of the device used in the invention.

FIG. 2 shows the left external carotid pulse and left dorsalis pedispulse recorded simultaneously with the STD Lead II of the ECG.

FIG. 3 is a schematic figure of a subject in the semi recumbent positionwith the sensors for the arterial pulses and electrodes for the ECG intheir proper places and connected to the oscilloscope and Oscillograph.

DETAILED DESCRIPTION OF THE INVENTION

As shown in FIG. 1, the device is a circular metallic plate onecentimeter in diameter and one millimeter thick in the center of whichis a solid tubular metallic rod one centimeter long and one millimeterin diameter whose free end is welded to the center of the pick upmicrophone of the NEP Pulse Recording Unit (Type-643) of Sanborn. Withthis attachment device placed on the skin directly over the arteries,pulses of the left external carotid and left dorsalis pedis arteries areobtained as shown in FIG. 2. FIG. 3 shows a subject in the semirecumbent position in a room with temperature controlled as constantlyas possible and the sensors placed over the left external carotid andleft dorsalis pedis artcrics. These pulses are recorded simultaneouslywith the STD Lead II of the ECG (FIG. 2). Recordings were made in somesubjects at intervals of six, twelve and eighteen months and the resultswere the same. Referring to FIG. 2, Q is the start of the isometricventricular contraction, A is the foot point of the anacrotic pulse ofthe left external carotid artery and A-1 is the foot point of theanacrotic pulse of the left dorsalis pedis artery. The time interval QAis the time the pulse travels from the left ventricle to the leftexternal carotid artery point and the time interval QA-1 is the time thepulse travels from the left ventricle to the left dorsalis pedis arterypoint. Therefore, the difference between the time intervals QA-1 and QAis a measure of the time delay between the instant the pulse is recordedfrom the “central artery”, i.e., the left external carotid artery andthe instant that the pulse is recorded from the “peripheral artery”,i.e., the left dorsalis pedis artery. This method is non invasive,simple, easy and fast to perform, reproducible and relativelyinexpensive. Its results are similar to more sophisticated and expensivemethods. It is very applicable for mass screening of big populations(normals and high risk individuals) especially in developing countries.

I claim:
 1. A new and original non-invasive method of indirectlydetermining the elasticity of the arterial wall in a subject which hasnot been mentioned in the medical literature up to present comprisingthe steps of: a) making use of a patient's left external carotid arteryas a “central artery” and the patient's left dorsalis pedis as a“peripheral artery”; b) attaching a metallic plate on a pick-upmicrophone of a high frequency oscillograph; c) placing the metallicplate directly on the patient's skin over the left external carotidartery and the left dorsalis pedis; d) recording arterial pulses of theleft external carotid and the left dorsalis pedis arteries using theoscillograph for a period of time; and e) getting a difference betweenthe arterial pulses to measure a time interval between the instant thatthe pulse is recorded from the “central artery” and the instant that thesame pulse is recorded from the “peripheral artery”.